In the art of magnetic resonance imaging, it is known to characterize mechanical properties of human or animal tissue by magnetic resonance rheology (cf. for instance to Muthipillai R. et al., Magnetic resonance imaging of acoustic strain waves, Proc. Soc. Magn. Reson. Nice, 1:189, 1995). In magnetic resonance rheology, the tissue is driven to mechanically oscillate during magnetic resonance imaging, which leads to effects causing an imaging contrast due to differences in tissue viscosity or elasticity. Low-frequency mechanical waves are coupled into the tissue and are visualized via a magnetic resonance sequence. The obtained additional information can be used, for instance, to distinguish healthy from malign tissue.
A number of different mechanical transducers for applying the mechanical oscillations to the tissue have been proposed, such as electromagnetic designs, which make use of the main magnetic field B0 inside the magnetic resonance scanner. Further, piezo-driven transducers or pneumatic designs were proposed for clinical application. In general, any mechanical transducer that appears to be suitable to the one skilled in the art may be employed.
Conventionally, magnetic resonance rheology examinations are carried out with a mechanical transducer that is statically attached to a subject of interest, for instance by strapping it around the subject of interest, or such that the subject of interest is lying on the mechanical transducer. An example of a conventional oscillation applicator for use in magnetic resonance rheology is shown in FIG. 5. The conventional oscillation applicator comprises a housing 96, which encompasses a mechanical transducer, and a piston 98 that is provided for transferring mechanical oscillations to the subject of interest. Dimensions of conventional oscillation applicators are about 50 millimeters in height with a footprint of about 100×100 mm2.
Further, the paper ‘MR elastography of the head and neck: Driver design and initial results’ by D. K. W. Yeung in Magn.Res.Imag. 31(2013)624-629 discloses a driver for MR elastography. This known driver comprises a tranducer embedded in a foam slab. The transducer has a protruding piston and a coil mounted at one of the piston. A headrest mould is positioned over the transducer and an opening opposing the centre of the piston is cut from the mould.